乏燃料容器坠落事故工况下核燃料厂房的安全性分析

Safety analysis on a nuclear fuel plant building under the condition of a spent fuel container dropping accident

根据核电厂的工艺布置,设计时需要考虑乏燃料容器可能发生的坠落事故对厂房结构的影响。为保证厂房整体结构和乏燃料水池的安全,在乏燃料容器可能的坠落位置铺设一定厚度的蒸压加气混凝土(AAC)砌体作为减振层是一种有效的防护措施。应用ANSYS/LS-DYNA对落锤冲击试验进行了有限元模拟,标定了AAC的材料模型参数,进而建立厂房的实体-分层壳有限元模型,模拟了乏燃料容器坠落对厂房整体结构的冲击动力响应,并从混凝土主应变、乏燃料水池跨中挠度以及楼层反应谱三个方面进行了安全性分析。结果表明:乏燃料容器坠落时,5 m厚度的AAC砌体能很好地吸收冲击能量,保证厂房整体结构的安全,坠落冲击处楼板和侧墙出现局部损伤,临近的乏燃料水池应力水平很低,但在部分频段楼层反应谱超出设备的设计输入值,需对设备作进一步验算。

According to the technological arrangement of a nuclear power plant,impact response effects of a fuel container dropping accident on the fuel plant building should be considered in the design. In order to ensure the safety of the nuclear power plant structure and the spent fuel pool,it is an effective measure to lay an AAC (autoclaved aerated concrete) masonry with a certain thickness to absorb the impact energy at the areas where the spent fuel container may drop. First,the hammer impact test of the AAC block was simulated to calibrate the parameters of the constitutive model MAT96 by using the ANSYS/LS-DYNA. Then,a FE(finite element)model of the whole fuel plant building was set up using solid elements and layered shell elements,and the impact response of the building under the condition of the spent fuel container dropping was analysed. Finally,from the aspects of the principal strain of concrete,the deflection of spent fuel pool and the floor response spectrum,a safety analysis of the whole fuel plant building was conducted. The results show that the AAC buffer layer with the thickness of 5 meters can effctively guarantee the safety and function of the building with slabs at the dropping position and surrounding walls slightly damaged and the spent fuel pool still well preserved. With regard to the equipments in the spent fuel pool,the floor impact response spectrum may exceed the design responce spectrum at certain frequency scope. So further special checking calculations of the equipments should be carried out.